Both dehydrogenation and dehydrocyclization processes include C—H bond activation and subsequent cleavage. The rather strong C—H bond activation is an a priori difficult problem. In a hydrocarbon molecule there are present several C—H bonds and as all C—H bonds are approximately equivalent in bond energy, it is difficult obtain high selectivity in dehydrogenation and dehydrocyclization reactions. The alkenes generated during dehydrogenation undergo further dehydrogenating conversions to form condensation products which are poor in hydrogen content. These products are precursors of carbonaceous deposits usually referred to as “coke”. Coke deposition deactivates the catalyst; therefore its activity and selectivity change over time. Preventing coke formation is one of the main problems in hydrocarbon processing.
Because of active coking, both dehydrogenation and dehydrocyclization as conventional reforming processes are carried out at feed dilution by hydrogen or steam at evident preponderance of diluent (molar proportion is up to 5:1). The effect of this diluent probably consists in elimination of freshly formed coke as a result of its hydrogenation or steam conversion. Feed dilution, i.e. low feed concentration, in reaction the zone decreases the degree of conversion and requires an increase of contact time, for example by pressure increase in the reaction apparatus. Increased hydrogen pressure decreases the amount of coke that is deposited but promotes hydrocracking and hydrogenolysis side reactions. An undesirable effect of both the increase in total pressure and in hydrogen pressure is the decrease of both dehydrogenation and dehydrocyclization reactions, as reactions that are carried out with increase of particles number and with hydrogen elimination. In real reforming processes at the most 15-20% of alkanes in feed are converted. Besides, reforming feed undergoes additional pretreatment for removal of: catalytic poisons (usually sulfur compounds); unconverted pentanes; and alkenes deactivating of catalyst.
A catalyst of dehydrogenation and dehydrocyclization of alkanes containing aluminum chromate (5-60 mass % in recalculation on Cr2O3) on the support (see Patent of Russian Federation No. 492115, Intern'l Class B01J 23/26, published Jan. 27, 2002) is known.
Shortcomings of this known catalyst are the considerable feedstock losses on coking and gas (hydrogen and light hydrocarbons).
The method of preparation of the catalyst of alkanes dehydrogenation and dehydrocyclization included deposition of active phase in the form of aluminum chromate on preliminary calcined alumina, or on a product of hydrargillite dehydration (see patent of Russian Federation No. 677168, Intern'l Class B01J 21/04, CO7C 5/32, is published Apr. 10, 2001).
The use of the catalyst prepared by this known method, results, as stated above, in considerable losses of feedstock on coking and gas.
A catalyst of hydrocarbons conversion including in % mass: nickel oxide 10.5-13.5; oxide of titanium 0.2-0.6; oxide of boron 0.3-0.9 and alumina—the rest (see Patent of Russian Federation No. 2157730, Intern'l Class B01J 37/02, B01J 23/755, published Oct. 20, 2000) is known.
Shortcomings of this known catalyst lie in the major losses of feedstock, undesirable formation of coke and light hydrocarbons, sensitivity to sulfur compounds and impossibility to use it in alkene-containing feed.
The method of preparation of this catalyst of hydrocarbons conversion is based in impregnation of the support in solution of nickel and aluminum nitrates and calcination of catalyst mass at 400-500° C. The support is prepared by molding of mixture including alumina, titanium hydride, boric acid and technical carbon with addition of mixture of paraffin, wax and oleinic acid as a binder, by casting at overpressure 0.4-0.2 mPa and temperature 70-75° C. with subsequent sun-curing and calcination (see Patent of Russian Federation No. 2157730, Intern'l Class B01J 37/02, B01J 23/755, published Oct. 20, 2000).
At hydrocarbons conversion over this catalyst prepared by the known method, considerable feed losses on formation of coke and gas, catalyst deactivation by formed coke and decrease of an inter-regeneration cycle is observed.
Carbon based catalysts for C—H bond activation have not been extensively studied. B. L. Moldavskii with coworkers found catalytic activity of carbon materials, specifically activated carbon and coke, in dehydrocyclization of n-octane or diisobutyl (2.5-dimethylhexane) and cyclohexane dehydrogenation at temperature of 500 to 560° C. and liquid hourly space velocity (LHSV) 0.1-0.15 h−1. In addition to this reactions, cycloalkane cracking actively occurred (see B. Moldavskii, F. Bezprozvannaya, G. Kamusher and M. Kobyl'skaya, Zhurnal Obshchei Khimii, 1937, b. 7, No. 13, p.p. 1840-1847).
Shortcoming of the known catalyst is the low activity, which is further slowed down during processing time, likely in connection with coke formation. The feedstock dilution by hydrogen does not inhibit of coking.
One of this catalysts is coke produced by pyrolysis of straight-run gasoline at 600° C. (see B. Moldavskii, F. Bezprozvannaya, G. Kamusher and M. Kobyl'skaya, Zhurnal Obshchei Khimii, 1937, b. 7, No. 13, p.p. 1840-1847).
A known catalyst for reforming of naphta, which consisted of petroleum hydrocarbons having more than 6 carbon atoms and not containing alkenes, was represented by activated carbon without treatment or one after impregnation in carbonates or hydroxides of alkali metals (Na, K, Li) and was used at temperature range 538-593° C. The treatment of activated carbon by carbonates and hydroxides of alkali metals decreased coking velocity and enabled catalyst regeneration (see R. A. Sanford and B. S. Friedman, Reforming with Carbon Catalysts, Ind. Eng. Chem., 1954, v.46, No. 12, p.p. 2568-2571).
The shortcoming of this known catalyst include low (not more than 20%) conversion grade, poor activity of treated catalyst in dehydrogenation reaction (the toluene yield from methylcyclohexane is 15.1%) and in dehydrocyclization process (toluene yield from n-heptane is 9.6%) and impossibility of inhibiting coking. So, at the feed dilution by hydrogen or steam at the molar proportion of diluent/hydrocarbon equal to 2.4, feed losses are equal to 2.3% by mass.
The entire carbon based catalyst rapidly lose activity with increased space velocity that is connected with coking and decrease of catalyst specific surface (see N. I. Shuikin, T. I. Naryshkina, Doklady Akademii Nauk SSSR, 1960, b. 135, No. 1, p.p. 105-108).
A catalyst for aromatization of n-hexane and n-octane based on composition of ZrO2 and carbon, prepared by sol-gel technique (see H. Preiss, L.-M. Berger, K. Szulzewsky. —Carbon. —1996, V.34, No. 1, p. 109-119) with subsequent calcination at different temperatures in He atmosphere is known. The most preferred catalyst sample with respect to catalytic activity was characterized by specific surface 141 m2/g, hydrogen adsorption (desorption) 92-93 μmole/g and ammonia desorption 0.21 mmole/g.
The aromatization of n-hexane and n-octane over this known catalyst was carried out only in hydrogen but not nitrogen atmosphere. n-Hexane conversion grade at its aromatization amounted to 20.7%, selectivity with respect to benzene—66.7%. The comparable amounts of alkane C1-C4 and alkene C2-C4, methylpentenes and methylcyclopentene in gas phase were observed. n-Octane conversion occurred more actively: conversion grade amounts to 35.5%, selectivity with respect to aromatics consisting mainly in comparable amounts of ethylbenzene and xylene was equal 91.2% (see D. L. Hoang, H. Preiss, B. Parlitz, F. Krumeich, H. Lieske, Appl. Catal. A. General, 1999, V.182, N 2, P. 385-397; A. Trunschke, D. L. Hoang, J. Radnik, K.-W. Brzezinka, A. Bruckner, H. Lieske, Appl. Catal. A. General, 2001, V.208, N2, P. 381-392).
The shortcomings of this known catalyst are its low (not more than 35.5%) alkane conversion grade, necessity of feed dilution by hydrogen in view of coking and impossibility of its use for aromatization of cyclohexane and its homologs.
Catalytic cracking, mainly with formation of alkane C1-C4 and alkene C2-C4 and n-octane isomerization occurred on a catalyst calcined at high temperature and containing zirconium oxycarbonyl.
It is necessary to point that carbonic catalysts are operated as a rule at higher (>500° C.) temperatures than those for known industrial reforming catalyst (450-470° C.) and have low isomerization activity.
A catalyst for dehydrogenation and hydrogenation of hydrocarbons including hydrogenolysis accepted as prototype based on fullerenes of the common formula Cn, where n=50-120, has been known. The catalyst is dissolved in a feed or dissolved in an appropriate solvent (see U.S. Pat. No. 5,336,828, Intern'l Class C07C 5/327, US Class 585/654, is published Aug. 9, 1994; U.S. Pat. No. 5,420,371, Intern'l Class C07C 005/03; C07C 005/10, US Class 585/266, published May 30, 1995).
The method of production of catalyst based on fullerene mixture included evaporation of carbon or graphite in the chamber at inert gas pressure 200 Torr by means of ohmic heat and concentrated solar radiation to surface temperatures 3000 to 4000° C., fullerene soot collection from chamber wall or its evacuation from inert gas and subsequent extraction of fullerene from fullerene soot by organic solvent accepted as prototype is known (see Patent of France 2710049, Inter'l Class C01B 31/00, is published Mar. 24, 1995).
The use of this catalyst in a solution inhibits insoluble products formation specifically coke. This known catalyst is active only in dehydrogenation of hydroaromatics but not that of alkanes. The applicability of the known catalyst for dehydrogenation of cyclohexane and its homologs is unknown, which makes the use of the known catalyst for alkane dehydrocyclization near to impossible. The fullerene sublimation decreased the usable temperature of known catalyst. The formation of stable fullerene hydride places in doubt the possibility of dehydrogenation of hydroaromatics with high conversion grade. The experiments show that fullerene and its epoxides catalyze alkane cracking but not alkane dehydrogenation.
Process of conversion of n-hexane to benzene over Cr2O3—Al2O3—Na2O catalyst in temperature range 550-580° C., pressure range 300-1500 Torr, hydrogen/hydrocarbon molar proportion equal to 3/1 and liquid hourly space velocity of feed in the range 0.2-2.0 h−1 is known (see Patent of Great Britain 1009511, Intern. Class C07C 5/00, is published Nov. 10, 1965).
The known method shortcomings are need of feed delution by hydrogen, low feed conversion degree, big feed dissipation on coke and gas that amount to 15.3%, concerned with that catalyst deactivation and increase of its activity that overcome by process temperature increase.
The process of petroleum feed processing (see U.S. Pat. No. 5,013,423, Intern. Class C10G 35/06, is published May 7, 1991) wherein the feed is contacted with non-acid dehydrogenation catalyst in hydrogen presence at the process condition (temperature, pressure and feed space velocity) that suffices for dehydrocyclization is known. The catalyst contains metal of platinum group on zeolite support with ZSM-5 type structure containing of indium. The product obtained at process temperature more than 427° C. in hydrogen presence have both more high octane number and aromatics content than initial reforming feed.
The known process shortcomings is low feed conversion degree, high benzene content (25-30%) in the end product, catalyst coking and needs of feed delution by hydrogen.
The process of pentane fraction processing with production of liquefied petroleum gas at direct interaction over acidic crystalline aluminosilicate with silicate module more than 12 having peak temperature of hydrazin desorption more than 650° C. (see Japan Patent by application No 3-54717, Intern. Class C10G May 11, 1993) is known.
The known process shortcomings are need of separation and utilization of by-products obtained in amount up to 12 vol. % and progressive catalyst coking with variable during process time products content and absence of dehydrogenation, dehydrocyclization or cracking of feed.
The process of conversion of heavy hydrocarbon (see RF Application 97107731, Intern. Class C10G 47/32, B01J 23/78, is published May 20, 1999) inclusive a supply of heavy hydrocarbon feed into reaction zone and feed conversion over catalytically active phase. Catalytically active phase includes first metal (not noble metal of group VIII) and second metal (alkali metal). The contacting of initial feed with a steam at a pressure≦2.1 mPa to produce hydrocarbons with decreased boiling temperature is realized in the known process. The first metal is selected from group include iron, cobalt, nickel or mixture of it, second metal is selected from group composed of potassium, sodium or its mixture. At least one from metals is fixed on support. The support is mesoporous, selected from group composed of silica, natural or synthetic aluminosilicates, aluminium oxides, petroleum cokes, coals or carbon base material obtained from vegetable or animal substance.
The known process shortcomings are feed cracking, the need of its delution, steam conversion of feed with syngas formation, progressive coking and catalyst deactivation concerned with that.
The process of processing of hydrocarbon feed based on aliphatic hydrocarbons (see RF Patent 2152977, Intern. Class C10G 35/095, is published Jul. 20, 2000) inclusive a supply of feed into reaction zone, delution of it by hydrocarbon gas and process realization at elevated temperature in preference 320-420° C. over silica-alumina catalyst with subsequent separation of end products. Aluminocobaltmolybdenic zeolite-containing catalyst with composition (in % mass.) zeolite ZSM-11 (silicate module is 17-60) 15÷45, cobalt oxide 2÷6, molibdenum oxide 8÷14 and a binder as catalyst is used. Sweet natural gas is used as hydrocarbon gas-deluent and process carries out at pressure 1.5-2.0 mPa to produces catalysate inclusive end aromatics and C1-C5 hydrocarbons with subsequent isolation of hydrocarbon fraction used as addition elevating gasoline octane number or high octane gasoline and liquefied C3-C4 hydrocarbons.
The known process shortcomings are the need of insertion of deluent natural gas with its previous pretreating (desulfurization or hydrofining) that complicates of process, high pressure of process carried out with particles number increase that causes feed conversion degree decrease, the need of pentanes removal from feed, the impossibility of conversion of alkenes and cycloalkanes or feed inclusive it and catalyst susceptibility to sulfur compounds conventional poisons.
The process of reforming of naphta consisted of petroleum hydrocarbons having more than 6 carbon atoms and not containing alkenes contained in the use activated carbon without treatment or one after impregnation in carbonates or hydroxides of alkali metals (Na, K, Li) as the catalyst at temperature range 538-593° C., is known. The treatment of activated carbon by carbonates and hydroxides of alkali metals decreases coking velocity and enable catalyst regeration (see R. A. Sanford and B. S. Friedman, Reforming with Carbon Catalysts, Ind. Eng. Chem., 1954, v.46, No. 12, pp. 2568-2571). The shortcoming of known process are low (not more than 20%) conversion grade, poor activity of treated catalyst in dehydrogenation reaction (the toluene yield from methylcyclohexane is 15.1%) and in dehydrocyclization process (toluene yield from n-heptane is 9.6%) and impossibility of coking inhibiting. So, at the feed delution by hydrogen or steam at the molar proportion diluent/hydrocarbon equal to 2.4 feed losses is equal 2.3% mass.
The process of dehydrogenation and hydrogenation of hydrocarbons including hydrogenolysis accepted as prototype (U.S. Pat. No. 5,336,828, Intern. Class C07C 5/327, is published Aug. 9, 1994) inclusive feed contacting with the catalyst representing at least one dissoluble fullerenes Cn, where n=50-120 at reaction mixture thermostating in temperature ranging 25-500° C. and pressure ranging 1-1500 Torr has been known. Named fullerene has been dissolved in the feed if the feed is liquid able to dissolve of fullerene or in additional solvent that is solvent for hydrocarbons too. The use of the catalyst in the form of solution is impeded of coke formation in the known process-prototype.
The shortcoming of known process-prototype are following. The known catalyst is active in hydroaromatics dehydrogenation only but not in alkane hydrogenation. The usefulness of known catalyst for dehydrogenation of cyclohexane and its homologs is unknown that excludes of use of known catalyst for alkane dehydrocyclization. Fullerene sublimation (S. K. Mathews, M. Sai Baba et al. Fullerene Science and Technology. 1993. No 1 (1). P. 101-109; M. V. Korobov, L. N. Sidorov, J. Chem. Termodynamics. 1994. V.26. P. 61-73) decreases temperature of use of known catalyst and constricts the field of reactions that are possible by thermodynamics.
So, both fullerene and its epoxides catalyze the cracking of alkanes but not its dehydrogenation. The formation of stable fullerene hydrides by the heating of mixture of fullerene and hydroaromatics causes of doubt about validity of possibility of dehydrogenation of hydroarmatics with high conversion degree.